Adjustable current-responsive device



July 2, 1968 c. L. JENCKS ETAL 3,

ADJUSTABLE CURRENT-RESPONSIVE DEVICE Filed Dec] 5, 1966 //V VE/V TORS C HA RLES L. damn/(s, GEORGE W. /(/SL BY W04? 9 A T TOR/v5 FIGS United States Patent 3,391,361 ADJUSTABLE CURRENT-RESPONSIVE DEVICE Charles L. Jencks, Avon, and George W. Kiesel, Unionville, Conn., assignors to General Electric Company, a corporation of New York Filed Dec. 5, 1966, Ser. No. 599,253 8 Claims. (Cl. 335-476) Our invention relates to adjustable current-responsive devices, and particularly to adjustable current-responsive devices suitable for use in electric circuit breakers to cause tripping of the circuit breaker upon the occurrence of predetermined current conditions therethrough.

Because of the varying needs of different applications, it is desirable that circuit breakers of the type referred to be provided with means whereby the user may adjust, within predetermined fixed limits, the particular current which will cause tripping, and particularly, tripping by electromagnetic means. For this reason, such circuit breakers are commonly provided with magnetic-trip adjusting means, which is accessible externally of the circuit breaker casing and movable by the user between predetermined fixed limits as determined by the physical configuration of the parts. Prior Patent 3,110,848, C. F. I-Iobson, Jr., issued Nov. 12, 1963, and assigned to the same assignee as the present invention, discloses a mechanism facilitating the construction and initial adjustment of such externally adjustable trip devices. In accordance with the aforesaid patent, a mechanism is disclosed such that when it is originally constructed and adjusted, if it is found that tripping does not occur at the desired current values at the high and low settings of the external adjustable member, such high and low settings may be adjusted to the desired value by internal adjustments, the high and low settings being adjustable without affecting the setting of the other. Thus, for example, common procedure in constructing and assembling such circuit breakers is to construct the device and then to test it to determine at what current tripping occurs when the adjusting knob is set at one extreme setting, such, for example, as the low setting. If tripping does not occur at the desired current at this setting, such for example as at 300% of the nominal current rating of the circuit breaker, the parts are adjusted, such for example, as by adjusting the air gap or adjusting the tension of the armature biasing spring, until tripping occurs at the desired point. The external adjusting knob is then turned to the opposite extreme setting, such for example as the high setting, and the breaker is again tested to determine what current is required to cause tripping. If it is found that tripping does not occur at the desired current level, such for example as at 500% of the nominal current rating, further adjustment must be performed to obtain tripping at this level.

In accordance with the art prior to the aforesaid Hobson patent, it would commonly be found that after making the required internal adjustments at the second or high setting, if the external knob is again returned to the low setting, it would be found that tripping no longer occurs at the previously adjusted level, but that would have been changed by the adjustments made in order to achieve tripping at the desired high setting. It would therefore be necessary to make further adjustments of the low setting, which in turn would have a lesser effect upon the previously adjusted high setting. Accordingly it was necessary to make repeated adjustments, and sometimes to comprise the desired settings at one or both extremes. In accordance with the aforesaid Hobson patent, however, a means is provided whereby the high and low settings may be adjusted independently, that is without changing the previously arrived at tripping current at the opposite setting. In subsequent Patent 3,391,361 Patented July 2, 1968 'ice No. 3,084,236, issued Apr. 2, 1963, to K. W. Klein and D. B. Powell and assigned to the same assignee as the present invention, an improved form of such independent high and low adjustment adjusting mechanism is disclosed.

It is an object of the present invention to provide an adjustable current-responsive device including a member movable between predetermined fixed limits of movement in which the high and low settings provided thereby are independently adjustable as in the aforesaid patents, and which is more compact than the aforesaid structures.

It is a further object of the invention to provide an adjustable current-responsive device of the type .described which is particularly suitable for use with rotary type externally adjustable means.

It is another object of the invention to provide an adjusting means of the type described requiring a minimum of pivoted interconnecting links.

It is a general object of the invention to provide an adjustable current-responsive device of the type described which is simple and inexpensive to construct.

In accordance with the the invention in one form, an electro-magnetic trip device is provided including a stationary magnetic field piece and a winding therefor, together with an armature movably mounted with respect to the field piece and biased to a normal attracted position by a biasing spring. Means is also provided for adjusting the tension of the biasing spring to adjust the pullin point of the magnetic armature. This adjusting means comprises anchor means for the end of the biasing spring and means for adjusting the anchor point comprising a pivoted lever. The position of the pivoted lever is determined by the engagement of the roller carried thereby and a cam surface of an adjusting member. As the adjusting member is moved, its cam surface acts on the roller to rotate the link carrying the anchor of the biasing spring and thereby changes the initial tension or length of the spring. In accordance with the invention, the adjusting member comprises a generally cylindrical member having one end thereof formed to provide a spiral cam surface. The slope of the spiral cam surface changes its angle with respect to the axis of rotation of the cylindrical member from the low to the high setting. The total amount of movement of the cam follower member produced by a complete rotation of the adjusting member depends on the radial distance of the cam follower member from the axis of rotation of the adjusting member. Thus, when the cam follower member is close to the axis of rotation of the adjusting member, a complete rotation produces very little movement of the cam follower member. On the other hand, when the cam follower member is positioned out at the periphery of the cam surface, a complete rotation of the adjusting member produces a substantial amount of movement of the cam follower member.

In accordance with another aspect of the invention, a portion of the cam surface is made to extend substantially at right angles to the axis of rotation of the adjusting member. At this setting, therefore, movement of the cam follower radially of the adjusting member does not change the position of the cam follower. Thus this setting is independent of such radial positioning, and the trip point at this setting may be adjusted by other suitable means such as by changing the length of a connecting link or adjusting the air gap, and the resulting setting will not be disturbed by the radial adjustment of the cam follower, which technique may then be used to independently adjust the other extreme setting.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

In the drawings,

FIGURE 1 is a side elevation view of an electric circuit breaker trip device incorporating the invention;

FIGURE 2 is a top plan view of the trip device of FIGURE 1;

FIGURE 3 is a perspective view of the adjusting cam member of the device of FIGURE 1;

FIGURES 4, 5 and 6 are fragmentary views of the trip device of FIGURES 1 and 2.

In the drawings, the invention is shown as incorporated in an electromagnetic trip device comprising a pair of supporting side plates 10 and 11 of nonmagnetic sheet metallic material supporting the remaining parts thereon and therebetween. A generally U-shaped magnetic field piece 12 is supported between the side plates 10 and 11 by suitable means such as by rivets 13, and is energized by a simplified winding of the single-turn type 14. The winding 14 consists of a single solid conductor passing through the magnetic field piece assembly. The particular embodiment illustrated is adapted for use with circuit breakers of relatively high rating, such for example as 2500 amperes.

A magnetic armature 15 is pivotally supported on a pivot pin 16 extending between the side plates 10 and 11 and is biased by a tension spring 17 to an unattracted normal position as determined by the stop pin 18 carried by the side plates 10 and 11. The armature 15 includes an extension 15A carrying an adjusting or calibrating screw 19.

One end of the spring 17 is connected to the armature 15, and the other end is connected to an adjustable anchor member 20 extending through a bent-up portion of an adjusting arm or link 21 pivotally supported on the plate 10 by means of a pivot pin 22. The anchor member 20 is adjustable with respect to the link 21 by means of an adjusting nut 20A. The link 21 also carries an adjustable stud 24 having a generally disc-shaped head portion 25 which engages a cam surface 26 of a generally cylindrical cam member 27. The stud member 24 is threadedly engaged in a cylindrical boss member 21A rigidly carried by the link 21 and extending outwardly through a suitable enlarged opening in the side plate 10. A lock nut 27B is provided for locking the position of the stud 24 with respect to the boss 21A.

The cam member 27 includes an integral flange portion 28, by means of which it is rotatably trapped between two cooperating members 29 and 30 which are fastened to inwardly directed flange portions 10A and 11A of the side portions 10 and 11 by suitable means such as by screws or rivets 31.

It will now be observed that rotation of the cam member 27 will cause the cam surface 26 to act on the head portion 25 of the stud 24 and cause rotation of the link 21 about its pivot point 22, thereby varying the tension of the Spring 17.

When the current in the winding 14 reaches a predetermined level, the armature 15 is attracted to the field piece 12, causing the calibrating screw 19 carried by the armature 15 to engage a cross-arm 35. The cross-arm is pivotally supported by an arm 36 mounted on the pivot 16 co-axially with the armature 15. The arm 36 carries an extension 36A projecting beyond the cross-arm 35 the end portion of which engages a projection 37 carried by a latch member 38 pivotally supported on a pivot pin 39 stationary with respect to the side frames 10 and 11. The latch member 38 is biased in clockwise direction by a compression spring 40, rotation in this direction being limited by a suitable stop pin 41. The latch member 38 includes a latch holding portion 42 which engages a releasable member 43 of the circuit breaker mechanism. When the armature 15 is attracted toward the field piece 12, the calibrating screw 19 engages the cross-arm 35, causing rotation of the arm 36 about its pivotal support 16 and causing the end portion 36A to engage the latch member 38 rotating it about its pivot pin 39 and withdrawing the latch projection 42 from the releasable member 43. This permits the circuit breaker mechanism to automatically separate contacts by suitable means, not shown. It will be understood that the circuit breaker trip device disclosed is suitable for use in multipole circuit breakers and that the cross-arm 35 may therefore extend across one or more similar trip devices, having correspondingly positioned arms 36, such that their armatures can engage the common trip bar to cause tripping of the latch member 38.

Adjustable cam construction The cam member 27 includes a projecting portion 45 of reduced diameter which in turn includes a radially extending integral projection 45A (see FIG. 2). The projection 45A engages an inwardly directed projection 29A of the support member 29. Because of the interengagement of these two projections, rotation of the cam member 27 is limited to slightly less than 360, such for example as a total of 330. In the embodiment shown, the maximum clockwise rotation of the cam member 27 as seen from the top determines the high position, that is, the position at which the highest amount of tension is exerted by the spring 17 and the greater amount of current is required to actuate the trip device. Conversely the maximum counterclockwise position of the cam member 27 determines the low position, that is the position at which the least amount of current is required to cause magnetic actuation.

In accordance with the invention, the cam member 27 is provided with an end-wise spiral type cam surface 48. The cam surface 48 includes a first portion 48A the surface of which extends substantially at right angles to the axis of rotation of the cam, as shown particularly in FIGURES 3 and 4. The cam surface 48 also includes an end portion 48B which extends at a relatively steep angle to the axis of rotation of the cam member 27 a shown particularly in FIGURE 5.

Operation and adjustment In operation, after the parts are assembled, the cam 27 is turned to the low position, as shown in FIGURE 4. This is the position in which the link member 21 is permitted to rotate counterclockwise the maximum amount, thereby permitting the spring 17 to shorten the maximum amount. This therefore represents the minimum length condition of the tension spring 17, and therefore the position at which a minimum amount of current is required to attract the armature 15 to the field piece 12. With the parts in this position, the device is tested to observe what amount of current is required to cause attraction of the armature 15 and tripping of the device. If this amount is other than the desired amount, the tension of the spring 17 at this position is adjusted by adjusting the anchor member 20 with respect to the link member 21, without changing the position of the cam member 27.

When the device has been adjusted to trip at the desired current level with the parts in the low position as described, the cam member 27 is turned to the opposite or high position. In this position, the cam surface 48 forces the head 25 of the stud 24 downwardly, rotating the link 21 clockwise about the pivot 22, and moving the anchor member 20 to the left as viewed in FIGURE 1, thereby increasing the tension of the spring 17, the parts then being in the position shown in FIG- URE 5. With the parts in the high position as shown in FIGURE 5, the device is again tested to observe what current is required to cause tripping of the device in this setting. If this current is other than the desired amount, the stud member 24 is adjusted axially so as to move the head 25 radially with respect to the cam surface 48 of the cam 27. Thus, for example, the stud 24 and head 25 are shown in one setting in FIGURES 4 and 5, and in a different adjusted setting in FIGURE 6. It should be observed that this adjustment is performed without changing the setting of the cam 27, which remains at the high setting. When the high setting has been adjusted as desired, no further adjustments are required. It will now be observed that when the parts are returned to the low position as shown in FIGURE 4, the position of the link 21, and therefore the length of the spring 17, will not have been changed from what they were when the parts were first adjusted with the stud member 24 in the solid line position shown in FIGURE 4, even though the stud may have been moved radially, such as to the position shown in dotted lines in FIGURE 4. This is made possible by the fact that the cam surface in the low setting extends substantially exactly at right angles to the axis of rotation of the cam 27 and therefore radial movement of the head 25 does not change the position of the link 21 and therefore the length of the spring 17. In order to facilitate radial movement of the head 25 of the stud 24, the edge portion of the head 25 is made rounded as shown. It will be appreciated that once the adjustments have been performed as described, there is no further need to change these internal adjustments, and the user is therefore referably not permitted access to these adjustments, which are within an outer insulating enclosure enclosing all of the parts shown, leaving access from the front to the portion 45 of the cam 27. If desired, nevertheless, the circuit breaker can obviously be readjusted at some later time to meet a different set of basic requirements by opening the enclosure and performing a readajustment of the anchor member 20 and subsequently of the stud 24.

While the invention has been described in only one specific embodiment, it will be readily apparent that many modifications thereof may be made. It is therefore intended by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United State is:

1. An adjustable current-responsive device including motion-transmitting means comprising:

(a) a support;

(b) a motion input member;

(0) means supporting said motion input member on said support for movement between first and second positions;

(d) said motion input member having a cam surface thereon;

(e) a motion output member;

(f) means movably supporting said motion output member on said support;

(g) a cam follower member carried by said motion output member;

(h) means retaining said cam follower member in engagement with said cam surface of said motion input member whereby the position of said output member is determined by the position of said input member;

(i) said cam surface having a first portion in engagement with said cam follower when said motion input member is in said first position and a second portion in engagement with said cam follower when said motion input member is in said second position, the portion of said cam surface between said first and second portions comprising a cam path extending in a predetermined direction and having a substantial width transversely of said predetermined direction;

(j) means supporting said cam follower member on I said motion output member for movement transversely of said predetermined cam path direction to selectively position said cam follower member at any one of a plurality of width-wise positions with respect to said cam surface, said cam surface having a different cam slope between said first and second positions corresponding to the path of engagement of said cam follower and said cam surface when said cam follower is at a different one of said width-wise positions, whereby the total movement of said cam follower member and said motion output member as said cam member is moved from said first to said second position is different for each of said plurality of width-wise positions of said cam follower member with respect to said cam surface.

2. An adjustable current-responsive device as set forth in claim 1, wherein said means supporting said cam follower member on said motion output member comprises means supporting said cam follower member for movement along a fixed path when moving transversely of said cam path direction and wherein said cam surface at said first portion has its width-wise dimension extending substantially parallel to said fixed path, whereby movement of said cam follower member transversely of said cam path when said motion input member is in said first position does not change the position of said motion output member, whereby the position of an adjusted member acted on by said motion-transmitting member may be adjusted at said first position of said motion input member without affecting the position of said adusted member at said second position of said motion input member.

3. An adjustable current-responsive device as set forth in claim 2, said means also comprising a motion-transmitting member carried by said motion output member, and means for adjusting the position of said motion transmitting member relative to said motion output member.

4. An adjustable current-responsive device as set forth in claim 1, wherein said motion input member comprises a cylindrical member supported for rotation about its longitudinal axis and said cam surface comprises an end face of said cylindrical member.

5. An adjustable current-responsive device as set forth in claim 4, wherein said first portion of said cam surface extends substantially perpendicular to said longitudinal axis in a direction transversely of said cam path.

6. An adjustable electromagnetic device comprising:

(a) a support;

(b) a magnetic field piece supported on said support;

(c) a magnetic armature movably supported on said support for movement between an unattracted position and an attracted position with respect to said field piece;

(d) spring means biasing said armature from said attracted to said unattracted position, said spring means having one end thereof engaging said armature;

(e) a cam follower link pivotally supported on said support;

(f) means connecting said cam follower link to said other end of said spring means;

(g) a cam follower member;

(h) means mounting said cam follower member on said cam follower link;

(i) a generally cylindrical cam member supported for rotation on said support about the longitudinal axis thereof;

(j) said cam member having one end surface thereof formed to provide a spiral type cam surface, said cam follower engaging said cam surface and determining the position of said cam follower link and thereby the bias of said biasing spring;

(k) said cam surface having the radial dimension thereof gradually changing its angular relationship to said axis of said cylindrical cam member from the beginning to the end of said cam surface;

(1) said means mounting said cam follower on said cam follower link comprising means for adjustably positioning said cam follower member to engage said cam surface selectively at any of a plurality of radially spaced positions on said cam surface.

7. An adjustable electromagnetic device as set forth in claim 6, wherein said device also comprises means for adjustably connecting said cam follower link to said biasing spring.

8. An adjustable electromagnetic device as set forth in claim 7, wherein said cam surface includes a portion thereof extending substantially exactly at right angles to said axis of rotation of said cylindrical member whereby said cam follower member may be adjusted radially with respect to said cam member at said location without changing the position of said cam follower link, and whereby the bias of said biasing spring may be adjusted to a desired value at said second setting of said cam member without affecting the setting of said biasing spring at said first location.

References Cited UNITED STATES PATENTS 2,915,683 12/1959 Lewus 335-274 3,084,236 4/1963 Klein et al. 33510 3,181,041 4/1965 Falk 335--176 10 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner. 

1. AN ADJUSTABLE CURRENT-RESPONSIVE DEVICE INCLUDING MOTION-TRANSMITTING MEANS COMPRISING: (A) A SUPPORT (B) A MOTION INPUT MEMBER; (C) MEANS SUPPORTING SAID MOTION INPUT MEMBER ON SAID SUPPORT FOR MOVEMENT BETWEEN FIRST AND SECOND POSITIONS; (D) SAID MOTION INPUT MEMBER HAVING A CAM SURFACE THEREON; (E) A MOTION OUTPUT MEMBER; (F) MEANS MOVABLY SUPPORTING SAID MOTION OUTPUT MEMBER ON SAID SUPPORT; (G) A CAM FOLLOWER MEMBER CARRIED BY SAID MOTION OUTPUT MEMBER; (H) MEANS RETAINING SAID CAM FOLLOWER MEMBER IN ENGAGEMENT WITH SAID CAM SURFACE OF SAID MOTION INPUT MEMBER WHEREBY THE POSITION OF SAID OUTPUT MEMBER IS DETERMINED BY THE POSITION OF SAID INPUT MEMBER; (I) SAID CAM SURFACE HAVING A FIRST PORTION IN ENGAGEMENT WITH SAID CAM FOLLOWER WHEN SAID MOTION INPUT MEMBER IS IN SAID FIRST POSITION AND A SECOND PORTION IN ENGAGEMENT WITH SAID CAM FOLLOWER WHEN SAID MOTION INPUT MEMBER IS IN SAID SECOND POSITION, THE PORTION OF SAID CAM SURFACE BETWEEN SAID FIRST AND SECOND PORTIONS COMPRISING A CAM PATH EXTENDING IN A PREDETERMINED DIRECTION AND HAVING A SUBSTANTIAL WIDTH TRANSVERSELY OF SAID PREDETERMINED DIRECTION; (J) MEANS SUPPORTING SAID CAM FOLLOWER MEMBER ON SAID MOTION OUTPUT MEMBER FOR MOVEMENT TRANSVERSELY OF SAID PREDETERMINED CAM PATH DIRECTION TO SELECTIVELY POSITION SAID CAM FOLLOWER MEMBER AT ANY ONE OF A PLURALITY OF WIDTH-WISE POSITIONS WITH RESPECT TO SAID CAM SURFACE, SAID CAM SURFACE HAVING A DIFFERENT CAM SLOPE BETWEEN SAID FIRST AND SECOND POSITIONS CORRESPONDING TO THE PATH OF ENGAGEMENT OF SAID CAM FOLLOWER AND SAID CAM SURFACE WHEN SAID CAM FOLLOWER IS AT A DIFFERENT ONE OF SAID WIDTH-WISE POSITIONS, WHEREBY THE TOTAL MOVEMENT OF SAID CAM FOLLOWER MEMBER AND SAID MOTION OUTPUT MEMBER AS SAID CAM MEMBER IS MOVED FROM SAID FIRST TO SAID SECOND POSITION IS DIFFERENT FOR EACH OF SAID PLURALITY OF WIDTH-WISE POSITIONS OF SAID CAM FOLLOWER MEMBER WITH RESPECT TO SAID CAM SURFACE. 